1. Field of the Invention
The invention relates to a method for manufacturing a light emitting device and a light emitting device.
2. Background Art
High-luminance light emitting devices having reduced light absorption by substrates have been obtained by growing a stacked unit as a crystal including a light emitting layer on a GaAs substrate, bonding to a transparent substrate made of GaP and the like, and subsequently removing the GaAs substrate.
In the case where an InGaAlP semiconductor is stacked on a GaAs substrate, it is easy to increase the doping efficiency to the p-type layers and suppress natural super lattices by using, for example, a substrate tilted from a (100) plane toward a [011] direction or a [01-1] direction.
Further, by matching the tilt of a GaP substrate to be bonded with the tilt of the GaAs substrate, a uniform bonding interface is provided, and it is easy to improve the electrical characteristics. Generally, the GaP substrate is formed by growing a crystal with a plane orientation of (100) or (111) using the LEC (Liquid Encapsulated Czochralski) method and tilting the crystal to the desired angle during the slicing process. In such a case, characteristic defects undesirably increase in the wafers sliced at a tilt for regions proximal to the seed portion and the tail portion because the doped impurities segregate from the seed side toward the tail side of the ingot.
One example discusses technology in which a substrate and a light emitting device configured for bonding are stably and closely adhered to an epitaxial growth layer formed on a substrate (JP-A 2008-252151 (Kokai)). In this example, a first epitaxial layer including an activation layer is formed on a first substrate. A second epitaxial layer is formed on a second substrate and integrally bonded to the first epitaxial layer. In the bonding process, a major surface of the first substrate predominantly exhibiting one selected from a (111) A plane and a (111) B plane is bonded to a major surface of the second substrate predominantly exhibiting the other selected from the (111) A plane and the (111) B plane.
However, it can be said that such technology does not sufficiently reduce fluctuation of characteristic distributions over the wafer after the bonding.